Disposable paper plates and similar containers are generally made from either pressed paperboard or molded pulp. Molded pulp containers, after drying, are strong and rigid but generally have rough surface characteristics. They are not usually coated and are susceptible to penetration by water, oil and other liquids. Pressed paperboard containers, on the other hand, can be decorated and coated with a liquid-resistant coating before being pressed by the forming dies into the desired shape.
General background with respect to pressed paperboard containers is seen in U.S. Pat. Nos. 5,203,491 entitled “Bake-In Press-Formed Container” of R. P. Marx et al.; 4,721,500 entitled “Method of Forming a Rigid Paper-Board Container” of G. J. Van Handel et al.; 4,721,499 entitled “Method of Producing a Rigid Paperboard Container” of R. P. Marx et al.; 4,609,140 entitled “Rigid Paperboard Container and Method and Apparatus for Producing Same” of G. J. Van Handel et al.; and 4,606,496 entitled “Rigid Paperboard Container” of R. P. Marx et al., all of which are incorporated herein by reference.
The following commonly-assigned patents and co-pending patent applications contain further information as to pressware materials, processing techniques and equipment and are also incorporated herein by reference: U.S. application Ser. No. 10/963,686, entitled “Pressed Paperboard Servingware with Improved Rigidity and Rim Stiffness”; U.S. application Ser. No. 10/600,814, entitled “Disposable Servingware Containers with Flange Tabs” (Publication No. US2004-0069788A1); U.S. Pat. No. 7,048,176, entitled “Deep Dish Disposable Pressed Paperboard Container”; U.S. Pat. No. 6,893,693, entitled “High Gloss Disposable Pressware”; U.S. Pat. No. 6,733,852, entitled “Disposable Serving Plate With Sidewall-Engaged Sealing Cover”; U.S. Pat. No. 6,715,630, entitled “Disposable Food Container With A Linear Sidewall Profile and an Arcuate Outer Flange”; U.S. Pat. No. 6,592,357, entitled “Rotating Inertial Pin Blank Stops for Pressware Die Sets”; U.S. Pat. No. 6,589,043, entitled “Punch Stripper Ring Knock-Out for Pressware Die Sets”; U.S. Pat. No. 6,585,506, entitled “Side Mounted Temperature Probe for Pressware Die Sets”; and U.S. Pat. No. 6,474,497, entitled “Smooth Profiled Food Service Articles”.
Equipment and methods for making paperboard containers are also disclosed in U.S. Pat. Nos. 5,249,946 entitled “Plate Forming Die Set” of R. P. Marx et al.; 4,832,676 entitled “Method and Apparatus for Forming Paperboard Containers” of A. D. Johns et al.; and 4,781,566 entitled “Apparatus and Related Method for Aligning Irregular Blanks Relative to a Die Half” of A. F. Rossi et al. In addition, applicant's co-pending U.S. patent application Ser. No. 11/057,959, entitled “Apparatus for Making Paperboard Pressware with Controlled Blank Feed” filed Feb. 15, 2005, discusses use of a variable speed blank feeder that includes a pervious feed belt, vacuum source and drive means.
The forming section of pressware apparatus may typically include a plurality of reciprocating upper die halves opposing, in facing relationship, a plurality of lower die halves. The upper die halves are mounted for reciprocating movement in a direction that is generally oblique or inclined with respect to the horizontal or vertical plane. The paperboard blanks, after cutting, are gravity fed to the inclined lower die halves in the forming section. The construction of the die halves and the equipment on which they are mounted may be substantially conventional; for example, as utilized on presses manufactured by the Peerless Machine & Tool Corporation, Marion, Ind. U.S. Pat. No. 4,435,143 entitled “Small Blank Feed and Tray Former” to Dempsey describes such apparatus. See also, U.S. Pat. No. 4,242,293 to Dowd. Optionally included are hydraulic controls as described in U.S. Pat. No. 4,588,539 to Rossi et al.
For paperboard plate stock of conventional thicknesses, i.e., in the range of from about 0.010 to about 0.040 inches, it is preferred that the spacing between the upper die surface and the lower die surface is as taught in U.S. Pat. Nos. 4,721,499 and 4,721,500. Note also the following patents of general interest with respect to forming paperboard containers: U.S. Pat. No. 6,527,687 to Fortney et al. which discloses a cut-in-place forming system with a draw ring and ejection means comprising air jets; U.S. Pat. No. 3,305,434 to Bernier et al. which discloses a paperboard forming apparatus; U.S. Pat. No. 2,832,522 to Schlanger which discloses another paperboard forming apparatus; and U.S. Pat. No. 2,595,046 to Amberg which discloses yet another paperboard forming apparatus.
It is conventional in the manufacture of pressed paperboard containers to feed paperboard blanks to a die set by way of gravity, that is, by passive means. “Active” feed techniques, where paperboard webs or blanks are supplied to the die set by means other than gravity, such as by belt or chain driven conveyors, are not generally employed due to their relative complexity and the need for close synchronization with the press. Pneumatic assist for pressing paperboard articles has heretofore generally been limited to assisting in product ejection, de-nesting or stripping from the mold, or in reducing friction during conveying from one processing station to another, and these functions have been accomplished with relatively simple air nozzles and the like. For example, in connection with ejection, de-nesting or stripping of pressed paperboard articles from a mold, the following patents are noted: U.S. Pat. No. 1,793,089 entitled “Paper Utensil Forming Die” to Heyes; U.S. Pat. No. 2,332,937 entitled “Molding Press” to Schmidberger; and U.S. Pat. No. 4,755,128 entitled “Apparatus for Releasing a Press-Formed Article From a Die Set” to Alexander et al. Pneumatic assists for ejection and de-nesting of other manufactured articles are found in U.S. Pat. No. 5,364,583 entitled “Method and Device for Removing an Injection-Molded Piece From a Mold” of Hayashi, and U.S. Pat. No. 5,693,346 entitled “Automatic Molded Hardboard Unnesting System” to Dull.
In connection with air cushioning or conveying of pressed paperboard articles previously cited U.S. Pat. Nos. 4,435,143 and 4,755,128 are noted. Air cushioning in connection with production of other types of articles are found in U.S. Pat. No. 4,741,196 entitled “Air Conveyor and Method for Removing Parts from a High Speed Forming Press” to Stewart, et al.; U.S. Pat. No. 5,017,052 entitled “Cup Conveyor” to Bartylla; U.S. Pat. No. 5,634,636 entitled “Flexible Object Handling System Using Feedback Controlled Air Jets” to Jackson et al.; U.S. Pat. No. 6,042,107 entitled “Device for Contact-Free Sheet Guidance in a Sheet-Fed Printing Press” to Stephan; and U.S. Pat. No. 6,585,259 entitled “Delivery of a Machine for Processing Flat Printing Materials” to Kerpe et al.
As to conveying equipment utilized in manufacturing operations generally, the following patents are noted: U.S. Pat. Nos. 5,945,137 to Mizuno et al.; 5,816,994 to Hill et al.; 5,163,891 to Goldsborough et al.; 5,074,539 to Wells et al.; 5,026,040 to Gibert; 4,748,792 to Jeffrey; 4,494,745 to Ward, Sr. et al.; 4,359,214 to Eldridge; and 3,228,066 to Rippstein.
It has been found in accordance with the present invention that paperboard blanks can be pneumatically propelled into a forming die by selective use of laminar air flow air knives to increase speed and reliability of the pressing operation. Air knives heretofore have been used in industrial processes primarily for drying applications. The apparatus and method of the invention eliminates moving parts as opposed to mechanical options for active blank feeding and thus requires less maintenance and capital investment as will be appreciated especially from the appended drawings.